PSA Undetectable in First Patient With mCRPC Given Cu-67 SAR-bisPSMA

The first patient with prostate cancer dosed with 2 cycles of 8GBq of 67Cu-SAR-bisPSMA has reached undetectable prostate specific antigen (PSA) levels using PET, according to Clarity Pharmaceuticals.¹

This patient is a part of cohort 2 of the ongoing SECuRE trial (NCT04868604) assessing 64Cu-SAR-bisPSMA and 67Cu-SAR-bisPSMA for metastatic castration-resistant prostate cancer (mCRPC) and received 2 cycles of 67Cu-SAR-bisPSMA at the 8 GBq dose level. The reduction in PSA level was from 47.2 ng/L at baseline to an undetectable level of less than 0.05 ng/ml.

In addition, the patient had undetectable lesions using PET post-treatment, 2 lesions showed a complete response, and 1 lesion showed a partial response. The lesion with a partial response only missed the complete response criteria by 2 millimeters, based on Response Evaluation Criteria In Solid Tumors (RECIST) assessment.

"As a clinician, there is nothing more rewarding than delivering the news to your patient that their cancer can no longer be detected, and with very few side effects following treatment, particularly for a patient that was heavily pre-treated with multiple lines of therapy, including androgen deprivation therapy [ADT], [androgen receptor pathway inhibition (ARPI)], chemotherapy and a [poly ADP ribose polymerase (PARP)] inhibitor and had failed all these treatments. For this patient who received 2 cycles of 67Cu-SAR-bisPSMA at 8 GBq, we have confirmed a near complete response through RECIST and have seen the result reflected in the reduction of PSA to an undetectable level and undetectable disease using PET,” said Luke Nordquist, MD, chief executive officer, urologic medical oncologist and principal investigator at the Urology Cancer Center/XCancer Omaha, Nebraska, in a press release.

SECuRE is a multicenter, single-arm, dose-escalation, cohort expansion, phase 1/2a theranostic trial for identification and treatment of PSMA-expressing mCRPC. Investigators aim to determine the safety and efficacy of 67Cu-SAR-bisPSMA for the treatment of patients with prostate cancer.²

Patients were heavily pre-treated with multiple lines of therapy, including ADT, ARPIs, chemotherapy and a PARP inhibitor, and had failed all previous treatments. Two cycles of 8 GBq 67Cu-SAR-bisPSMA were given to the patient. The initial cycle followed the SECuRE trial protocol, and the second cycle was provided under the FDA expanded access program (EAP).

Further findings showed that the patient experienced 3 adverse events (AEs), most of which were mild. All the AEs have been resolved. Additionally, there have been no dose-limiting toxicities observed among any of the 12 patients treated in the SECuRE trial to date.

Recruitment is ongoing for cohort 3 which will evaluate treatment given at the highest single dose level of 12GBq.

“The EAP is giving us insights into the potential therapeutic benefit we might see from multiple doses of 67Cu-SAR-bisPSMA, and the early data is showing that 67Cu-SAR-bisPSMA may one day provide cancer patients with an effective and safe alternative for those in need. I believe 67Cu-SAR-bisPSMA presents a new opportunity for cancer patients to have an effective result with few [adverse] effects," added Nordquist.¹

REFERENCES:

1. First patient with metastatic prostate cancer to receive 2 doses of Cu-67 SAR-bisPSMA achieves undetectable PSA level. News release. Clarity Pharmaceuticals. November 30, 2023. Accessed November 30, 2023. https://tinyurl.com/5n8zks7n

2. 64Cu-SAR-bisPSMA and 67Cu-SAR-bisPSMA for identification and treatment of PSMA-expressing metastatic castrate resistant prostate cancer (SECuRE) (SECuRE). ClinicalTrials.gov. Updated October 12, 2023. Accessed November 30, 2023. https://clinicaltrials.gov/study/NCT04868604